Enhanced physical downlink control channel scrambling and demodulation reference signal sequence generation

ABSTRACT

Methods, apparatuses, and systems are described to provide enhanced physical downlink control channel scrambling and demodulation reference signal sequence generation.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to: U.S. Provisional PatentApplication No. 61/679,627 filed 3 Aug. 2012 and entitled “AdvancedWireless Communication Systems and Techniques”; U.S. ProvisionalApplication No. 61/692,597 filed 23 Aug. 2012 and entitled “AdvancedWireless Communication Systems and Techniques”; U.S. Provisional PatentApplication No. 61/707,784 filed 28 Sep. 2012 and entitled “AdvancedWireless Communication Systems and Techniques”; and U.S. ProvisionalPatent Application No. 61/721,436 filed 1 Nov. 2012 and entitled“Advanced Wireless Communication Systems and Techniques,” the entiredisclosures of which are hereby incorporated by reference in theirentireties.

FIELD

Embodiments of the present invention relate generally to wirelessnetworks and more particularly to enhanced physical downlink controlchannel scrambling and demodulation reference signal sequencegeneration.

BACKGROUND

In existing 3GPP LTE networks, downlink control information (DCI) may bescrambled using a scrambling sequence that is specific to a userequipment (UE). However, there may be situations in which a UE otherthan the target UE successfully de-scrambles and decodes DCI that wasdirected to the target UE. In these situations, the UE may incorrectlyact on the DCI causing errors or other inefficiencies.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. To facilitatethis description, like reference numerals designate like structuralelements. Embodiments are illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings.

FIG. 1 schematically illustrates a high-level example of a networksystem comprising a UE and an eNB, in accordance with variousembodiments.

FIG. 2 illustrates components of a UE and an eNB, in accordance withvarious embodiments.

FIG. 3 illustrates subframes for cell A and B, in accordance withvarious embodiments.

FIG. 4 illustrates receive circuitry in accordance with variousembodiments

FIGS. 5-7 illustrate example UE-RS patterns for an EPDDCH using normalCP, in accordance with various embodiments.

FIG. 8 illustrates a method in accordance with various embodiments.

FIG. 9 schematically illustrates an example system that may be used topractice various embodiments described herein.

DETAILED DESCRIPTION

Illustrative embodiments of the present disclosure include, but are notlimited to, methods, systems, computer-readable media, and apparatusesfor enhanced physical downlink control channel scrambling anddemodulation reference signal sequence generation.

Various aspects of the illustrative embodiments will be described usingterms commonly employed by those skilled in the art to convey thesubstance of their work to others skilled in the art. However, it willbe apparent to those skilled in the art that alternate embodiments maybe practiced with only some of the described aspects. For purposes ofexplanation, specific numbers, materials, and configurations are setforth in order to provide a thorough understanding of the illustrativeembodiments. However, it will be apparent to one skilled in the art thatalternate embodiments may be practiced without the specific details. Inother instances, well-known features are omitted or simplified in ordernot to obscure the illustrative embodiments.

Further, various operations will be described as multiple discreteoperations, in turn, in a manner that is most helpful in understandingthe illustrative embodiments; however, the order of description shouldnot be construed as to imply that these operations are necessarily orderdependent. In particular, these operations need not be performed in theorder of presentation.

The phrase “in some embodiments” is used repeatedly. The phrasegenerally does not refer to the same embodiments; however, it may. Theterms “comprising,” “having,” and “including” are synonymous, unless thecontext dictates otherwise.

The phrase “A and/or B” means (A), (B), or (A and B). The phrases “A/B”and “A or B” mean (A), (B), or (A and B), similar to the phrase “Aand/or B.”

As used herein, the term “circuitry” refers to, is part of, or includeshardware components such as an Application Specific Integrated Circuit(ASIC), an electronic circuit, a logic circuit, a processor (shared,dedicated, or group) and/or memory (shared, dedicated, or group) thatare configured to provide the described functionality. In someembodiments, the circuitry may execute one or more software or firmwareprograms to provide at least some of the described functionality.

FIG. 1 schematically illustrates a network environment 100 in accordancewith various embodiments. The network environment 100 includes a userequipment (UE) 104 wirelessly coupled with an evolved Node B (eNB) 108of a radio access network (RAN) via an over-the-air (OTA) interface. TheRAN may be part of a 3GPP LTE Advanced (LTE-A) network and may bereferred to as an evolved universal terrestrial radio access network(EUTRAN). In other embodiments, other radio access network technologiesmay be utilized.

The UE 104 may include a communication device 112 that implementsvarious communication protocols in order to effectuate communicationwith the eNB 108. The communication device 112 may be a chip, chipset,or other collection of programmed and/or preconfigured circuitry. Insome embodiments, the communication device 112 may include or be part ofbaseband circuitry, a radio-frequency circuitry, etc.

The communication device 112 may include control circuitry 114 thatperforms various control operations related to communication over theRAN. These control operations may include, determining uplink controlinformation, resource allocation, etc. The control circuitry 114 mayinclude radio resource control layer 116 and may be coupled with, andcontrol operation of, transceiver circuitry 120, which is, in turn,coupled with one or more antennas 124.

The eNB 108 may have similar components such as communication device122, control circuitry 126, RRC layer 128, transceiver circuitry 132,and one or more antennas 136. The control circuitry 124 may also includea reference signal (RS) generator 140.

FIG. 2 illustrates Tx circuitry 200 and Rx circuitry 204, which may beincluded in transceiver circuitry 132 and 120, respectively, inaccordance with some embodiments. The Tx circuitry 200 and Rx circuitry204 may be used to transmit and receive enhanced physical downlinkcontrol channel (EPDCCH) transmissions. EPDCCH transmissions may carrydownlink control information that includes resource assignments andother control information for a UE or a group of UEs. Each EPDCCHtransmission may include one or more enhanced control channel elements(ECCEs).

The Tx circuitry 200 may include a cyclic redundancy check (CRC)generating and masking circuitry 220 that may receive bits, for example,downlink control information (DCI) bits, generate CRC bits and appendthe CRC bits to the DCI bits, and mask the DCI+CRC bit sequence. Themasking of the DCI+CRC bit sequence may be based on a radio networktemporary identity (RNTI) of a user equipment that is the intendedrecipient of the ePDCCH transmission. In one embodiment, CRC bits may beadded to DCI bits and the resulting sequence may be masked based onRNTI₁, which is associated with UE₁.

The Tx circuitry 200 may further include encoding circuitry 212 toreceive the masked bit sequence and encode the sequence with a selectedchannel encoding scheme. The channel encoding scheme may be a ReedMuller (RM) code, a dual RM code, a quad RM code, a tail-bitingconvolutional code (TBCC), a turbo code, etc. The encoding circuitry 212may also perform rate matching, for example, virtual circular bufferrate matching. Given a 56 DCI bits, 16 CRC bits, and a 1/2 code rate,the encoding circuitry 212 may output a 144-bit encoded sequence.

The Tx circuitry 200 may further include scrambling circuitry 216 toreceive and scramble the encoded bit sequence to provide a scrambled bitsequence. The scrambling circuitry scrambling may be based on a cellidentifier.

The encoded bit stream, may be scrambled according to{tilde over (b)}(i)=(b(i)+c(i))mod 2,  Equation 1

where {tilde over (b)}(i) is the scrambled bit sequence, b(i) is theencoded bit sequence, and c(i) is a scrambling sequence, e.g., apseudo-random sequence (for example, a Gold sequence, pseudo-noise (PN)sequence, Kasami sequence, etc.).

The scrambling circuitry 216 may include a scrambling sequence generatorthat provides the scrambling sequence. The scrambling sequence generatormay be initialized with an initialization seed c_(int) at a start ofeach subframe to generate the scrambling sequence c(i). Theinitialization seed may be a cell-specific seed given by:c _(int) =└n _(s)/2┘*2⁹ +N _(ID) ^(cell),  Equation 2

where n_(s) is a slot number within a radio frame varying from 0 to 19,and N_(ID) ^(cell) may be an initialization seed parameter such as acell identifier.

In coordinated multipoint (CoMP) scenarios, the initialization seedparameter may be a virtual cell identifier, for example, N_(ID)^(ePDCCH), and may be assigned by a high layer. For example, RRC layer128 may configure scrambling circuitry 216 with the virtual cellidentifier. In embodiments in which more than one EPDCCH set is used,for example, two EPDCCH sets, the configured virtual cell identifier maybe given as N_(ID,i) ^(ePDCCH) for the EPDCCH transmission in EPDCCH seti. Thus, the initialization seed parameter corresponds to the EPDCCHset. In some embodiments, the virtual cell ID for EPDCCH set i may bethe same as what is used for UE-specific RS initialization associatedwith EPDCCH.

In some embodiments, if a virtual cell ID is not configured, theinitialization seed parameter may be a physical cell identifier.

The block of scrambled bits {tilde over (b)}(0), . . . , {tilde over(b)}(M_(bit)−1) may be modulated by modulating circuitry 220 using, forexample, QPSK modulation. This may result in a block of complex-valuedsymbols d(0), . . . , d(M_(symb)−1) where M_(symb)=M_(bit)/2=2N_(sc)^(RB), where N_(sc) ^(RB) is a number of subcarriers in a resource blockand may equal 12. The complex-valued symbols may be transmitted, overchannel 222, to the Rx circuitry 204.

The block of complex-valued symbols may be received by demodulatingcircuitry 224 of the Rx circuitry 204. Demodulating circuitry 224 maydemodulate the block of complex-valued symbols to provide a block ofscrambled bits.

The Rx circuitry 204 may further include descrambling circuitry 228coupled with the demodulating circuitry 224 to receive and descramblethe block of scrambled bits to provide the encoded bit sequence. Thedescrambling circuitry 228 may descramble the block of scrambled bitsbased on cell ID. If the cell ID is a virtual cell ID it may bepredetermined or be provided to the descrambling circuitry 228 by RRClayer 116. If the cell ID is a physical cell ID, the control circuitry114 may derive the value based on primary and secondary synchronizationsignals broadcast by the eNB 108. If the cell ID used by thedescrambling circuitry 228 matches the cell ID used by the scramblingcircuitry 216, the bits will be properly descrambled.

The Rx circuitry 204 may further include decoding circuitry 232 coupledwith the descrambling circuitry 228 to receive and decode the encodedbit sequence to provide the DCI+CRC bit sequence.

The Rx circuitry 204 may further include demasking and CRC checkingcircuitry 236 coupled with the decoding circuitry 232 to de-mask the bitsequence and remove and check the CRC bits. The de-masking may be basedon an RNTI of the receiving device, for example, the UE 104. If the RNTImatches that used in the masking operation, the bit sequence may beregarded properly. The DCI bits may then be transmitted to higher-layersof, for example, the control circuitry 114.

Using the cell ID as the initialized seed, rather than a UE identifier,such as RNTI, may result in less false alarms that could result from aUE that is not the intended recipient correctly descrambling anddecoding DCI.

While the description details DCI transmission on EPDCCH a similartransmit process, including scrambling based on cell identifier, may beused for other transmissions such as, but not limited to, transmissionof user-specific demodulation reference signals (UE-RS) associated withthe EPDCCH.

The RS generator 140 may generate a UE-RS that may be transmitted froman antenna port at the eNB 108 to enable the UE 104 to derive a channelestimate for the data transmitted by the antenna port. An antenna portmay correspond to one or more physical transmit antennas; however, asignal transmitted by an antenna port may be designed such that it isnot further deconstructed by a receiver.

In some situations, interference measured from a UE-RS may not matchinterference experienced by EPDCCH resource elements (REs) subsequentlytransmitted by the same antenna port. This may be due to frequencydivision multiplexed (FDM)/code division multiplexed (CDM) ECCEs beingassociated with completely overlapped FDM/CDM UE-RS.

Inter-cell interference mismatch may be explained as follows. Assumecell A uses UE-RS antenna port 7 to transmit ECCE 0 to UE 1 and aneighbor cell B uses UE-RS antenna port 8 to transmit eCCE 1 to UE 2.The received signals from a pair of orthogonal cover code having lengthof 2, (OCC-2) REs are listed as:

$\begin{matrix}\left\{ {\begin{matrix}{y_{0} = {{x_{0}*1*H_{0}} + {x_{2}*1*H_{1}}}} \\{y_{1} = {{x_{1}*1*H_{0}} + {x_{3}*\left( {- 1} \right)*H_{1}}}}\end{matrix},} \right. & {{Equation}\mspace{14mu} 3}\end{matrix}$

where x₀ and x₁ are reference signal sequences on first and second UE-RSREs for cell A, x₂ and x₃ are reference signal sequences on first andsecond UE-RS REs for cell B, H₀ and H₁ are channels from cell A and cellB to UE 1, and y₀ and y₁ are the received signals on the first andsecond UE-RS REs.

In order to remove the potential mismatched intra-cell interference, UE1 may first descramble, using descrambling circuitry 228, for example,and then do OCC-2 decoding, using decoding circuitry 232, for example,by usingy=y ₀*1*x ₀ ^(T) +y ₁*1*x ₁ ^(T) =H ₀+(x ₂ *x ₀ ^(T) −x ₃ *x ₁ ^(T))H₁.  Equation 4

Based on Equation 4 and FIG. 3, which illustrates subframes for cell Aand cell B in accordance with an embodiment, it may be seen that the DCImay not experience intercell interference but UE-RS of Equation 4includes the inter-cell interference, represented by the term “(x₂*x₀^(T)−x₃*x₁ ^(T))H₁”. This results in interference mismatch and maydegrade performance.

The potential mismatched inter-cell interference may be removed if thefollowing equation is satisfied:x ₂ *x ₀ ^(T) −x ₃ *x ₁ ^(T)=0.  Equation 5

Equation 5 may be satisfied when a common scrambling sequence is usedfor both REs of a pair of OCC-2 UE-RS REs, which may result in x₀=x₁ andx₂=x₃.

When using the same scrambling sequence for both REs of a pair of OCC-2UE-RS REs, for an antenna port p in a physical resource block n_(PRB)assigned for an associated EPDCCH, the modulating circuitry 220 may mapat least part of a reference signal sequence r(m) to complex-valuedmodulation symbols a_(k,l) ^((p)) in a subframe, using normal cyclicprefix according to:

$\begin{matrix}{a_{k,l}^{(p)} = {{w_{p}\left( l^{\prime} \right)} \cdot {r\left( {{3 \cdot \left\lfloor \frac{l^{\prime}}{2} \right\rfloor \cdot N_{RB}^{\max,{DL}}} + {3 \cdot n_{PRB}} + m^{\prime}} \right)}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

where, N_(RB) ^(max,DL) is a maximum number of downlink resource blocksgiven system bandwidth;

$\begin{matrix}{{w_{p}(i)} = \left\{ {{\begin{matrix}{{\overset{\_}{w}}_{p}(i)} & {{\left( {m^{\prime} + n_{PRB}} \right)\mspace{14mu}{mod}\; 2} = 0} \\{{\overset{\_}{w}}_{p}\left( {3 - i} \right)} & {{\left( {m^{\prime} + n_{PRB}} \right)\mspace{14mu}{mod}\; 2} = 1}\end{matrix}k} = {{{5\; m^{\prime}} + {N_{sc}^{RB}n_{PRB}} + {k^{\prime}k^{\prime}}} = \left\{ {{\begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {p \in \left\{ {9,10,12,14} \right\}}\end{matrix}l} = \left\{ {{\begin{matrix}{{l^{\prime}\mspace{14mu}{mod}\; 2} + 2} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 3},4,8,{{or}\mspace{14mu} 9^{*}}} \\{{l^{\prime}\mspace{14mu}{mod}\; 2} + 2 + {3\left\lfloor {l^{\prime}/2} \right\rfloor}} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1},2,6,{{or}\mspace{14mu} 7^{*}}} \\{{l^{\prime}\mspace{14mu}{mod}\; 2} + 5} & {{if}\mspace{14mu}{not}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}}\end{matrix}l^{\prime}} = \left\{ {{{\begin{matrix}{0,1,2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0\mspace{14mu}{and}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7^{*}}} \\{0,1} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0\mspace{14mu}{and}\mspace{14mu}{not}\mspace{14mu}{in}\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7^{*}}} \\{2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {1\mspace{14mu}{and}\mspace{14mu}{not}\mspace{14mu}{in}\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7^{*}}}\end{matrix}m^{\prime}} = 0},1,2} \right.} \right.} \right.}} \right.} & \; \\{{\,^{*}{See}}\mspace{14mu}{Table}\mspace{14mu} 4.2\text{-}1\mspace{14mu}{of}\mspace{14mu} 3{GPP}\mspace{14mu}{TS}\mspace{14mu} 36.211\mspace{14mu} v\; 10.5{.0}\;\left( {{June}\mspace{14mu} 2012} \right)\mspace{14mu}{for}\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{{configurations}.}} & \;\end{matrix}$

The sequence w _(p)(i) for normal cyclic prefix may be given by Table 1.

TABLE 1 Antenna port p [w _(p)(0) w _(p)(1) w _(p)(2) w _(p)(3)] 7 [+1+1 +1 +1] 8 [+1 −1 +1 −1] 9 [+1 +1 +1 +1] 10 [+1 −1 +1 −1] 11 [+1 +1 −1−1] 12 [−1 −1 +1 +1] 13 [+1 −1 −1 +1] 14 [−1 +1 +1 −1]

Given that Equation 6 uses the same scrambling sequence for a pair ofOCC-2 UE-RS REs, there may be some impact on inter-cell interferencerandomization on UE-RS REs. This may be overcome by applying a UE-RSport-specific scrambling sequence depending on how many UE-RS antennaports n_(p) are used. This may result in Equation 6 being modified tobe:

$\begin{matrix}{a_{k,l}^{(p)} = {{w_{p}\left( l^{\prime} \right)} \cdot {{r\begin{pmatrix}{\left( {p\mspace{14mu}{mod}\mspace{14mu} n_{p}} \right) \cdot 6 \cdot N_{RB}^{\max,{DL}} \cdot 3 \cdot} \\{{\left\lfloor \frac{l^{\prime}}{2} \right\rfloor \cdot N_{RB}^{\max,{DL}}} + {3 \cdot n_{PRB}} + m^{\prime}}\end{pmatrix}}.}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

Note that a maximum pseudo-random sequence length may be defined for aUE-RS as 12*N_(RB) ^(max,DL). In order to meet the antenna port specificlength of 8 UE-RS antenna ports in Equation 7, the maximum sequencelength of one embodiment may be 12*n_(p)*N_(RB) ^(max,DL). That is, theUE-RS sequence r(m) can be generalized to cover up to 8 antenna ports,for example, n_(p)=8, as follows:

$\begin{matrix}{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2*{c\left( {2\; m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {{1 - {2*{c\left( {{2\; m} + 1} \right)}}},\mspace{79mu}{{{where}m} = \left\{ {\begin{matrix}{0,1,\ldots\mspace{14mu},{{96\; N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{128\; N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}\end{matrix}.} \right.}} \right.}}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

The pseudo-random sequence c(i) may be defined as described above and insome embodiments the scrambling sequence generator of the scramblingcircuitry 216 may be initialized with:

$\begin{matrix}{{c_{int} = {{\left( {\left\lfloor \frac{n_{s}}{2} \right\rfloor + 1} \right)*\left( {{2N_{ID}^{cell}} + 1} \right)*2^{16}} + n_{SCID}}},} & {{Equation}\mspace{14mu} 9}\end{matrix}$

where N_(ID) ^(cell) is a physical cell ID or a virtual cell ID and mayindicate one of multiple transmission points when used in a CoMPscenario. For example, EPDCCH set 0 may be transmitted from cell #0 withN_(ID) ^(cell#0) and EPDCCH set 1 may be transmitted from cell #1 withN_(ID) ^(cell#1). In another example, EPDCCH set 0 and EPDCCH set 1 maybe transmitted from cell #0 (or cell #1) with N_(ID) ^(cell#0) (orN_(ID) ^(cell#1)). The value of n_(SCID) may be a constant value (forexample, 0, 1, 2, . . . ). For a PDSCH transmission on antenna ports 7or 8, n_(SCID) may be given by a DCI format 2B or 2C associated with thePDSCH transmission. In the case of DCI format 2B, n_(SCID) may beindicated by a scrambling identity field.

If number of antenna ports is up to 2 (for example, antenna port 7 and8), for example, n_(p)=2, the UE-RS sequence r(m) may be given byEquation 8 where

$m = \left\{ \begin{matrix}{0,1,\ldots\mspace{14mu},{{24N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{32N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{{prefix}.}}\end{matrix} \right.$

FIG. 4 illustrates Rx circuitry 400 in accordance with some embodiments.The Rx circuitry 400 may include a channel estimation circuitry 404 andcompensation circuitry 408 and may be configured to addressorthogonality issues that may be observed with the residual interferencewhen a UE tries to estimate a channel for an antenna port by ade-spreading operation from OCC. Embodiments described below may reducethe residual interference.

FIGS. 5-8 illustrate example UE-RS patterns for an EPDDCH using normalCP in accordance with some embodiments. In particular, FIG. 5illustrates a UE-RS pattern 504 for antenna port 7 with special subframeconfigurations 1, 2, 6, or 7; a UE-RS pattern 508 for antenna port 7with special subframe configurations 3, 4, or 8; and a UE-RS pattern 512for antenna port 7 with all other downlink subframes. FIG. 6 illustratesa UE-RS pattern 604 for antenna port 8 with special subframeconfigurations 1, 2, 6, or 7; a UE-RS pattern 608 for antenna port 8with special subframe configurations 3, 4, or 8; and a UE-RS pattern 612for antenna port 8 with all other downlink subframes. FIG. 7 illustratesa UE-RS pattern 704 for antenna port 9 with special subframeconfigurations 1, 2, 6, or 7; a UE-RS pattern 708 for antenna port 9with special subframe configurations 3, 4, or 8; and a UE-RS pattern 712for antenna port 9 with all other downlink subframes. FIG. 8 illustratesa UE-RS pattern 804 for antenna port 10 with special subframeconfigurations 1, 2, 6, or 7; a UE-RS pattern 808 for antenna port 10with special subframe configurations 3, 4, or 8; and a UE-RS pattern 812for antenna port 10 with all other downlink subframes.

For antenna ports p=7, p=8, or p=7, 8, . . . , v+6, in a PRB with afrequency-domain index n_(PRB) assigned for a corresponding PDSCHtransmission, a part of the RS sequence r(m) may be mapped tocomplex-valued modulation symbols modulation symbols a_(k,l) ^((p)) in asubframe, with normal CP, according to Equation 6, 7, ora _(k,l) ^((p)) =w _(p)(l′)·r(3·l′·N _(RB) ^(max,DL)+3·n _(PRB)+m′).  Equation 10

For localized EPDCCH, multiple-user (MU) MIMO may allow two UEs to sharethe same PRBs. In this case, two different antenna ports (for example,antenna ports 7 and 8) distinguished by CDM can be used for channelestimation for each UE. For example, antenna port 7 may be used bychannel estimation circuitry of UE #0 and antenna port 8 may be used bychannel estimation circuitry of UE #1 in order to estimate each channel.A pair of OFDM symbols, e.g., OFDM symbols 0, sharing the same resourcebut distinguished by CDM may be referred to as a CDM group. The channelestimation circuitry may determine which symbols of a CDM group aredirected to respective UEs by performing a de-spreading operation basedon an orthogonal cover code.

In some embodiments, a scrambling sequence generator of the scramblingcircuitry 216, for example, may generate UE-RS for EPDCCH on antennaports 7-10 by:

$\begin{matrix}{{c_{int} = {{\left( {\left\lfloor \frac{n_{s}}{2} \right\rfloor + 1} \right)*\left( {{2X} + 1} \right)*2^{16}} + n_{SCID}}},} & {{Equation}\mspace{14mu} 11}\end{matrix}$

where X may be a virtual cell ID that is provided as a UE-specific RRCparameter with a range of 0-503 for an EPDCCH set. The channelestimation circuitry 404 may descramble the UE-RS using the virtual cellID similar to that described above with respect to descramblingcircuitry 228 descrambling the DCI.

If UE #0 uses antenna port 7 with X=X0 and UE #1 uses antenna port 8with X=X1, the received signals for two adjacent OFDM symbols may berepresented as follows:R ₀ =C ₀ ^(UE#0) ·W ₇(0)·H ^(UE#0) +C ₀ ^(UE#1) ·W ₈(0)·H^(UE#1)  Equation 12R ₁ =C ₁ ^(UE#0) ·W ₇(1)·H ^(UE#0) +C ₁ ^(UE#1) ·W ₈(1)·H^(UE#1),  Equation 13

where: R₀ is a received signal at OFDM symbol 0; R₁ is a received signalat OFDM symbol 1; C₀ ^(UE#0) is a reference signal sequence at OFDMsymbol 0 for UE #0 (initialized by X=X0); C₁ ^(UE#0) is a referencesignal sequence at OFDM symbol 1 for UE #0 (initialized by X=X0); C₀^(UE#1) is a reference signal sequence at OFDM symbol 0 for UE #1(initialized by X=X1); C₁ ^(UE#1) is a reference signal sequence at OFDMsymbol 1 for UE #1 (initialized by X=X1); W₇(0) is a Walsh code forantenna port 7 at OFDM symbol 0 (W₇(0)=+1); W₇(1) is a Walsh code forantenna port 7 at OFDM symbol 1 (W₇(1)=+1); W₈(0) is a Walsh code forantenna port 8 at OFDM symbol 0 (W₈(0)=+1); W₈(1) is a Walsh code forantenna port 8 at OFDM symbol 1 (W8(1)=−1); H^(UE#0) is a channel for UE#0 experienced at antenna port 7; and H^(UE#1) is a channel for UE #1experienced at antenna port 8.

It may be assumed that the channels for a UE in adjacent OFDM symbolsare the same and a noise/interference term is omitted for ease ofexplanation. In some embodiments, channel estimation circuitry, forexample channel estimation circuitry 404, may estimate H^(UE#0) atantenna port 7 for UE #0 by using the following receiver process:{tilde over (H)} ^(UE#0) =R ₀·(C ₀ ^(UE#0))*·(W ₇(0))*+R ₁·(C ₁^(UE#0))*·(W ₇(1))*,  Equation 14wherein (.)* is a complex conjugate operation.

The channel estimation circuitry 404 may estimate H^(UE#1) at antennaport 8 for UE #1 by using the following receiver process:{tilde over (H)} ^(UE#1) =R ₀·(C ₀ ^(UE#1))*·(W ₈(0))*+R₁·(C ₁^(UE#1))*·(W ₈(1))*  Equation 15

From equations 12 and 13, equations 14 and 15 respectively becomeequations 16 and 17:

$\begin{matrix}{{2 \cdot {\overset{\sim}{H}}^{{UE}{\# 0}}} = {{{R_{0} \cdot \left( C_{0}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(0)} \right)^{*}} + {R_{1} \cdot \left( C_{1}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(1)} \right)^{*}}} = {{{\left( {{C_{0}^{{UE}{\# 0}} \cdot {W_{7}(0)} \cdot H^{{UE}{\# 0}}} + {C_{0}^{{UE}{\# 1}} \cdot {W_{8}(0)} \cdot H^{{UE}{\# 1}}}} \right) \cdot \left( C_{0}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(0)} \right)^{*}} + {\left( {{C_{0}^{{UE}{\# 0}} \cdot {W_{7}(1)} \cdot H^{{UE}{\# 0}}} + {C_{1}^{{UE}{\# 1}} \cdot {W_{8}(1)} \cdot H^{{UE}{\# 1}}}} \right) \cdot \left( C_{1}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(1)} \right)^{*}}} = {{{2 \cdot H^{{UE}{\# 0}}} + \left( {{C_{0}^{{UE}{\# 1}} \cdot {W_{8}(0)} \cdot H^{{UE}{\# 1}} \cdot \left( C_{0}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(0)} \right)^{*}} + {C_{1}^{{UE}{\# 1}} \cdot {W_{8}(1)} \cdot H^{{UE}{\# 1}} \cdot \left( C_{1}^{{UE}{\# 0}} \right)^{*} \cdot \left( {W_{7}(1)} \right)^{*}}} \right)} = {{2 \cdot H^{{UE}{\# 0}}} + \left( {{C_{0}^{{UE}{\# 1}} \cdot H^{{UE}{\# 1}} \cdot \left( C_{0}^{{UE}{\# 0}} \right)^{*}} - {C_{1}^{{UE}{\# 1}} \cdot H^{{UE}{\# 1}} \cdot \left( C_{1}^{{UE}{\# 0}} \right)^{*}}} \right)}}}}} & {{Equation}\mspace{14mu} 16} \\{{2 \cdot {\overset{\sim}{H}}^{{UE}{\# 1}}} = {{{R_{0} \cdot \left( C_{0}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(0)} \right)^{*}} + {R_{1} \cdot \left( C_{1}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(1)} \right)^{*}}} = {{{\left( {{C_{0}^{{UE}{\# 0}} \cdot {W_{7}(0)} \cdot H^{{UE}{\# 0}}} + {C_{0}^{{UE}{\# 1}} \cdot {W_{8}(0)} \cdot H^{{UE}{\# 1}}}} \right) \cdot \left( C_{0}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(0)} \right)^{*}} + {\left( {{C_{1}^{{UE}{\# 0}} \cdot {W_{7}(1)} \cdot H^{{UE}{\# 0}}} + {C_{1}^{{UE}{\# 1}} \cdot {W_{8}(1)} \cdot H^{{UE}{\# 1}}}} \right) \cdot \left( C_{1}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(1)} \right)^{*}}} = {{{2 \cdot H^{{UE}{\# 1}}} + \left( {{C_{0}^{{UE}{\# 0}} \cdot {W_{7}(0)} \cdot H^{{UE}{\# 0}} \cdot \left( C_{0}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(0)} \right)^{*}} + {C_{1}^{{UE}{\# 0}} \cdot {W_{7}(1)} \cdot H^{{UE}{\# 0}} \cdot \left( C_{1}^{{UE}{\# 1}} \right)^{*} \cdot \left( {W_{8}(1)} \right)^{*}}} \right)} = {{2 \cdot H^{{UE}{\# 1}}} + \left( {{C_{0}^{{UE}{\# 0}} \cdot H^{{UE}{\# 0}} \cdot \left( C_{0}^{{UE}{\# 1}} \right)^{*}} - {C_{1}^{{UE}{\# 0}} \cdot H^{{UE}{\# 0}} \cdot \left( C_{1}^{{UE}{\# 1}} \right)^{*}}} \right)}}}}} & {{Equation}\mspace{14mu} 17}\end{matrix}$

In order to estimate each channel by each UE, either of the followingconditions should be fulfilled to cancel out the interference terms.

-   Condition 1) C₀ ^(UE#0)=C₀ ^(UE#1) and C₁ ^(UE#0)=C₁ ^(UE#1)-   Condition 2) C₀ ^(UE#0)=C₁ ^(UE#0) and C₀ ^(UE#1)=C₁ ^(UE#1).

Thus, condition 1 provides that a reference signal sequence at a firstOFDM symbol for a first UE, using a first antenna port, is the same as areference signal sequence at a first OFDM symbol for a second UE, usinga second antenna port; and a reference signal sequence at a second OFDMsymbol for the first UE is the same as a reference signal sequence at asecond OFDM symbol for the second UE. With condition 1, the equations 16and 17 respectively become equations 18 and 19:2·{tilde over (H)} ^(UE#0)=2·H ^(UE#0);   Equation 18and2·{tilde over (H)} ^(EU#1)=2·H ^(UE#1).  Equation 19

Condition 2, which may be implemented by Equation 10, provides that areference signal sequence at a first OFDM symbol for a first UE, using afirst antenna port, is the same as a reference signal sequence at asecond OFDM symbol for the first UE; and a reference signal sequence ata first OFDM symbol for a second UE, using a second antenna port, is thesame as a reference signal sequence at a second OFDM symbol for thesecond UE. With condition 2, the equations 19 and 20 respectively becomeequations 20 and 21:2·{tilde over (H)} ^(UE#0)=2·H ^(UE#0);   Equation 20and2·{tilde over (H)} ^(UE#1)=2·H ^(UE#1).  Equation 21

In this way, the channel estimation circuitries, e.g., channelestimation circuitry 404, may orthogonally estimate channels for each ofthe pair of UEs. The compensation circuitry 408 may receive an estimateof the channel from the channel estimation circuitry 404 and compensatea received signal (received from the channel estimation circuitry 404 orfrom elsewhere, e.g., an antenna). The compensated signal may betransmitted to other Rx circuitry, such as demodulating circuitry 224.

When condition 1 is implemented, the eNB 108 may pair MU-MIMO for twoUEs having same RS sequences. The channel estimation circuitry 404 mayassume that the same RS sequences are used for a pair of antenna ports,(for example antenna port 7 and antenna port 8) and may performde-spreading operation on a received MU-MIMO signal based on theassumption in order to receive a desired symbol of a CDM group.

In some embodiments, the UE 104 may perform blind decoding of the EPDCCHbased on the assumption that the same reference signal sequences r(m)are used at an RE within a CDM group (for example, antenna ports 7 and8, 9 and 10, 11 and 13, or 12 and 14). Blind decoding may be performedby the UE in an attempt to determine which ECCEs convey the EPDCCHintended for the UE.

FIG. 9 illustrates a method 900 of blind decoding in accordance with anembodiment.

At 904, the method 900 may include assuming a reference signal sequenceis same for pair of antenna ports. Thus, a reference signal sequencereceived for a first antenna port for communications between a UE and aneNB may also be used for communications of a second antenna port. Thecommunications of the second antenna port may be between the eNB andanother UE.

At 908, the method 900 may include estimating a channel. The estimatingof the channel may be based on the assumption of 904.

At 912, the method 900 may include compensating a channel. Thecompensating of the channel may be based on the estimating of 908.

At 916, the method 900 may include performing a blind decoding based onthe compensated channel (and therefore, based on the assuming that thereference signal sequence is the same for the first and second antennaports). The performing of the blind decoding may include monitoringEPDCCH candidates associated with one or more of the pair of antennaports.

The UE 104 and eNB 108 described herein may be implemented into a systemusing any suitable hardware and/or software to configure as desired.FIG. 10 illustrates, for one embodiment, an example system 1000comprising one or more processor(s) 1004, system control logic 1008coupled with at least one of the processor(s) 1004, system memory 1012coupled with system control logic 1008, non-volatile memory(NVM)/storage 1016 coupled with system control logic 1008, a networkinterface 1020 coupled with system control logic 1008, and input/output(I/O) devices 1032 coupled with system control logic 1008.

The processor(s) 1004 may include one or more single-core or multi-coreprocessors. The processor(s) 1004 may include any combination ofgeneral-purpose processors and dedicated processors (e.g., graphicsprocessors, application processors, baseband processors, etc.).

System control logic 1008 for one embodiment may include any suitableinterface controllers to provide for any suitable interface to at leastone of the processor(s) 1004 and/or to any suitable device or componentin communication with system control logic 1008.

System control logic 1008 for one embodiment may include one or morememory controller(s) to provide an interface to system memory 1012.System memory 1012 may be used to load and store data and/orinstructions, e.g., communication logic 1024. System memory 1012 for oneembodiment may include any suitable volatile memory, such as suitabledynamic random access memory (DRAM), for example.

NVM/storage 1016 may include one or more tangible, non-transitorycomputer-readable media used to store data and/or instructions, e.g.,communication logic 1024. NVM/storage 1016 may include any suitablenon-volatile memory, such as flash memory, for example, and/or mayinclude any suitable non-volatile storage device(s), such as one or morehard disk drive(s) (HDD(s)), one or more compact disk (CD) drive(s),and/or one or more digital versatile disk (DVD) drive(s), for example.

The NVM/storage 1016 may include a storage resource physically part of adevice on which the system 1000 is installed or it may be accessible by,but not necessarily a part of, the device. For example, the NVM/storage1016 may be accessed over a network via the network interface 1020and/or over Input/Output (I/O) devices 1032.

The communication logic 1024 may include instructions that, whenexecuted by one or more of the processors 1004, cause the system 1000 toperform operations associated with the components of the communicationdevice 112 or 122 as described with respect to the above embodiments. Invarious embodiments, the communication logic 1024 may include hardware,software, and/or firmware components that may or may not be explicitlyshown in system 1000.

Network interface 1020 may have a transceiver 1022 to provide a radiointerface for system 1000 to communicate over one or more network(s)and/or with any other suitable device. In various embodiments, thetransceiver 1022 may be integrated with other components of system 1000.For example, the transceiver 1022 may include a processor of theprocessor(s) 1004, memory of the system memory 1012, and NVM/Storage ofNVM/Storage 1016. Network interface 1020 may include any suitablehardware and/or firmware. Network interface 1020 may include a pluralityof antennas to provide a multiple input, multiple output radiointerface. Network interface 1020 for one embodiment may include, forexample, a wired network adapter, a wireless network adapter, atelephone modem, and/or a wireless modem.

For one embodiment, at least one of the processor(s) 1004 may bepackaged together with logic for one or more controller(s) of systemcontrol logic 1008. For one embodiment, at least one of the processor(s)1004 may be packaged together with logic for one or more controllers ofsystem control logic 1008 to form a System in Package (SiP). For oneembodiment, at least one of the processor(s) 1004 may be integrated onthe same die with logic for one or more controller(s) of system controllogic 1008. For one embodiment, at least one of the processor(s) 1004may be integrated on the same die with logic for one or morecontroller(s) of system control logic 1008 to form a System on Chip(SoC).

In various embodiments, the I/O devices 1032 may include user interfacesdesigned to enable user interaction with the system 1000, peripheralcomponent interfaces designed to enable peripheral component interactionwith the system 1000, and/or sensors designed to determine environmentalconditions and/or location information related to the system 1000.

In various embodiments, the user interfaces could include, but are notlimited to, a display (e.g., a liquid crystal display, a touch screendisplay, etc.), speakers, a microphone, one or more cameras (e.g., astill camera and/or a video camera), a flashlight (e.g., a lightemitting diode flash), and a keyboard.

In various embodiments, the peripheral component interfaces may include,but are not limited to, a non-volatile memory port, a universal serialbus (USB) port, an audio jack, and a power supply interface.

In various embodiments, the sensors may include, but are not limited to,a gyro sensor, an accelerometer, a proximity sensor, an ambient lightsensor, and a positioning unit. The positioning unit may also be partof, or interact with, the network interface 1020 to communicate withcomponents of a positioning network, e.g., a global positioning system(GPS) satellite.

In various embodiments, the system 1000 may be a mobile computing devicesuch as, but not limited to, a laptop computing device, a tabletcomputing device, a netbook, a smartphone, etc. In various embodiments,system 1000 may have more or less components, and/or differentarchitectures.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims and theequivalents thereof.

Some non-limiting examples are provide below.

Example 1 includes apparatus to be employed in an enhance node B (eNB),the apparatus comprising: scrambling circuitry to receive a bit sequencethat includes downlink control information (DCI) to be transmitted on anenhanced physical downlink control channel (EPDCCH) and to scramble thebit sequence based on a cell identifier to provide a scrambled bitsequence; and modulating circuitry coupled with the scrambling circuitryto receive the scrambled bits and to modulate the scrambled bits, with aquadrature phase shift keying modulation scheme, to provide a block ofcomplex-valued modulation symbols.

Example 2 includes the apparatus of example 1, wherein a scramblinginitialization seed includes the cell identifier, and the scramblingcircuitry is to scramble the DCI bits based on the scramblinginitialization seed.

Example 3 includes the apparatus of example 1, wherein the cellidentifier is a virtual cell identifier provided to the scramblingcircuitry by a radio resource control layer.

Example 4 includes the apparatus of example 3, wherein the DCI is to betransmitted in a first EPDCCH set, and the virtual cell identifiercorresponds to the first EPDDCH set.

Example 5 includes the apparatus of example 3, further comprising:

a reference signal (RS) generator to generate demodulation referencesignals associated with the EPDCCH based on the virtual cell identifier.

Example 6 includes the apparatus of example 1, wherein the cellidentifier is a physical cell identifier.

Example 7 includes the apparatus of any of examples 1-6, furthercomprising: cyclic redundancy check (CRC) generating and maskingcircuitry to generate a bit sequence that includes DCI and CRC bits andto mask the bit sequence based on a radio network temporary identity(RNTI) of a user equipment that is an intended recipient of the DCI.

Example 8 includes the apparatus of any of examples 1-5, wherein thecell identifier is configured by radio resource control (RRC) signaling.

Example 9 includes an apparatus to be employed in a user equipment, theapparatus comprising: demodulating circuitry to receive complex-valuedmodulation symbols of an enhanced physical downlink control channel(EPDCCH) set that include downlink control information (DCI) anddemodulate the complex-valued modulation symbols to provide a bitsequence; and descrambling circuitry coupled with the demodulatingcircuitry to descramble the bit sequence based on a initialization seedparameter that corresponds to the EPDCCH set to provide a descrambledbit sequence.

Example 10 includes the apparatus of example 9, wherein theinitialization seed parameter is a virtual cell identifier and thedescrambling circuit is configured to receive the virtual cellidentifier from a radio resource control layer.

Example 11 includes the apparatus of example 10, wherein thedemodulating circuitry is to receive complex-valued modulation symbolsof another EPDCCH set and demodulate the complex-valued modulationsymbols to provide another bit sequence; and the descrambling circuitryis to descramble the other bit sequence based on an initialization seedparameter that corresponds to the other EPDCCH set to provide anotherdescrambled bit sequence.

Example 12 includes the apparatus of example 9, wherein the cellidentifier is a physical cell identifier and the user equipment furthercomprises: control circuitry to: receive primary and secondarysynchronization signals from an evolved Node B (eNB); determine thephysical cell identifier based on the primary and secondarysynchronization signals; and provide the physical cell identifier to thedescrambling circuitry.

Example 13 includes the apparatus of any of examples 9-11, wherein thecell identifier is configured by radio resource control (RRC) signaling.

Example 14 includes an apparatus to be employed in an enhanced node B(eNB), the apparatus comprising: a reference signal (RS) generator togenerate an RS sequence to be transmitted on a pair of orthogonal covercode (OCC) user equipment reference signal (UE-RS) resource elements(REs); and scrambling circuitry to use a common scrambling sequence forboth REs.

Example 15 includes an apparatus of example 14, wherein the RS sequenceis r(m) and is given by:

${r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2*{c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {{1 - {2*{c\left( {{2m} + 1} \right)}}},{{{where}m} = \left\{ \begin{matrix}{0,1,\ldots\mspace{14mu},{{96N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{128N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{{prefix}.}}\end{matrix} \right.}} \right.}}$

Example 16 includes the apparatus of example 14, wherein the RS sequenceis r(m), is to be transmitted by 2 antenna ports, and is given by:

${r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2*{c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {{1 - {2*{c\left( {{2m} + 1} \right)}}},{{{where}m} = \left\{ \begin{matrix}{0,1,\ldots\mspace{14mu},{{24N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{32N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{{prefix}.}}\end{matrix} \right.}} \right.}}$

Example 17 includes the apparatus of example 14, further comprising:modulating circuitry to map at least part of the reference signalsequence r(m) to complex-valued modulation symbols a_(k,l) ^((p)) in asubframe, using normal cyclic prefix according to:

${a_{k,l}^{(p)} = {{w_{p}\left( l^{\prime} \right)} \cdot {r\left( {{3 \cdot \left\lfloor \frac{l^{\prime}}{2} \right\rfloor \cdot N_{RB}^{\max,{DL}}} + {3 \cdot n_{PRB}} + m^{\prime}} \right)}}},$where:N_(RB) ^(max,DL) is a maximum number of downlink resources elements in aresource block;

$\mspace{79mu}{{w_{p}(i)} = \left\{ {{{\begin{matrix}{{\overset{\_}{w}}_{p}(i)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 0} \\{{\overset{\_}{w}}_{p}\left( {3 - i} \right)} & {{{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 1} = 0};}\end{matrix}\mspace{79mu} k} = {{5m^{\prime}} + {N_{sc}^{RB}n_{PRB}} + k^{\prime}}};\mspace{79mu}{k^{\prime} = \left\{ {{\begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {{p \in \left\{ {9,10,12,14} \right\}};}\end{matrix}l} = \left\{ {{\begin{matrix}{{l^{\prime}{mod}\; 2} + 2} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 3},4,{8\mspace{14mu}{or}\mspace{14mu} 9}} \\{{l^{\prime}{mod}\; 2} + 2 + {3\left\lfloor {l^{\prime}/2} \right\rfloor}} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1},2,{6\mspace{14mu}{or}\mspace{14mu} 7}} \\{{l^{\prime}{mod}\; 2} + 5} & {{{if}\mspace{14mu}{not}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}};}\end{matrix}l^{\prime}} = \left\{ \begin{matrix}{0,1,2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0\mspace{14mu}{and}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,\mspace{11mu}{{or}\mspace{14mu} 7}} \\{0,1} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0{\mspace{11mu}\;}{and}\mspace{14mu}{not}\mspace{14mu}{in}{\mspace{11mu}\;}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{{or}\mspace{14mu} 7};{and}}} \\{2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {1{\mspace{11mu}\;}{and}\mspace{14mu}{not}{\mspace{11mu}\;}{in}\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7}}\end{matrix} \right.} \right.} \right.}} \right.}$

Example 18 includes the apparatus of any of examples 14-17, wherein thecommon scrambling sequence is based on a virtual cell identifier.

Example 19 includes the apparatus of example 18, further comprising: aradio resource control layer to provide the scrambling circuitry withthe virtual cell identifier.

Example 20 includes an apparatus to be employed in a user equipment, theapparatus comprising: channel estimation circuitry to receive areference signal sequence for a first antenna port on an orthogonalfrequency division multiplexing (OFDM) symbol, and estimate a channelfor the first antenna port for the UE based on the received referencesignal sequence and an assumption that the reference signal sequence istransmitted to another UE for a second antenna port; and channelcompensation circuitry coupled with the channel estimation circuitry toreceive an estimate of the channel and compensate a received signal.

Example 21 includes the apparatus of example 20, wherein the channelestimation circuitry is to perform a de-spreading operation on areceived signal based on the assumption.

Example 22 includes the apparatus of example 21, wherein thede-spreading operation is based on an orthogonal cover code.

Example 23 includes one or more computer-readable media havinginstructions that, when executed, cause a user equipment to: assume areference signal sequence received for a first antenna port forcommunications between the UE and an enhanced node B is also used forcommunications of a second antenna port; perform a blind decodingoperation for enhanced physical downlink control channel (EPDCCH) basedon said assumption.

Example 24 includes the one or more computer-readable media of example23, wherein the instructions, when executed, further cause the userequipment to: process the reference signal sequence for the firstantenna port on an orthogonal frequency division multiplexing (OFDM)symbol; and estimate a channel for the first antenna port for the UEbased on the reference signal sequence and assumption that the referencesignal sequence is also used for communications of a second antennaport.

Example 25 includes the one or more computer-readable media of example24, wherein the instructions, when executed, further cause the userequipment to: compensate a received signal based on the estimate of thechannel.

Example 26 includes an apparatus to be employed in a user equipment, theapparatus comprising: means for assuming a reference signal sequencereceived for a first antenna port for communications between the UE andan enhanced node B is also used for communications of a second antennaport; performing a blind decoding operation for enhanced physicaldownlink control channel (EPDCCH) based on said assumption.

Example 27 includes an apparatus of example 26, further comprising:means for processing the reference signal sequence for the first antennaport on an orthogonal frequency division multiplexing (OFDM) symbol; andmeans for estimating a channel for the first antenna port for the UEbased on the reference signal sequence and assumption that the referencesignal sequence is also used for communications of a second antennaport.

Example 28 includes the apparatus of example 26, further comprising:means for compensating a received signal based on the estimate of thechannel.

Example 29 a method comprising: receiving complex-valued modulationsymbols of an enhanced physical downlink control channel (EPDCCH) setthat include downlink control information (DCI) and demodulate thecomplex-valued modulation symbols to provide a bit sequence; anddescrambling the bit sequence based on a initialization seed parameterthat corresponds to the EPDCCH set to provide a descrambled bitsequence.

Example 30 includes the method of example 29, wherein the initializationseed parameter is a virtual cell identifier and the method furthercomprises receiving the virtual cell identifier from a radio resourcecontrol layer.

Example 31 includes the method of any of examples 29-30, wherein thecell identifier is configured by radio resource control (RRC) signaling.

Example 32 includes an apparatus to be employed in an enhanced node B(eNB), the apparatus comprising: means for generating an RS sequence tobe transmitted on a pair of orthogonal cover code (OCC) user equipmentreference signal (UE-RS) resource elements (REs); and means forscrambling both REs using a common scrambling sequence.

Example 33 includes the apparatus of example 32, wherein the RS sequenceis r(m) and is given by:

${r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2*{c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {{1 - {2*{c\left( {{2m} + 1} \right)}}},{{{where}m} = \left\{ {{\begin{matrix}{0,1,\ldots\mspace{14mu},{{96N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{128N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{{prefix}.}}\end{matrix}{or}{where}m} = \left\{ \begin{matrix}{0,1,\ldots\mspace{14mu},{{24N_{RB}^{\max,{DL}}} - 1}} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{0,1,\ldots\mspace{14mu},{{32N_{RB}^{\max,{DL}}} - 1}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{{prefix}.}}\end{matrix} \right.} \right.}} \right.}}$

Example 34 includes the apparatus of example 32, further comprising:modulating circuitry to map at least part of the reference signalsequence r(m) to complex-valued modulation symbols a_(k,l) ^((p)) in asubframe, using normal cyclic prefix according to:

${a_{k,l}^{(p)} = {{w_{p}\left( l^{\prime} \right)} \cdot {r\left( {{3 \cdot \left\lfloor \frac{l^{\prime}}{2} \right\rfloor \cdot N_{RB}^{\max,{DL}}} + {3 \cdot n_{PRB}} + m^{\prime}} \right)}}},$where:N_(RB) ^(max,DL) is a maximum number of downlink resources elements in aresource block:

$\mspace{79mu}{{w_{p}(i)} = \left\{ {{{\begin{matrix}{{\overset{\_}{w}}_{p}(i)} & {{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 2} = 0} \\{{\overset{\_}{w}}_{p}\left( {3 - i} \right)} & {{{\left( {m^{\prime} + n_{PRB}} \right){mod}\; 1} = 0};}\end{matrix}\mspace{79mu} k} = {{5m^{\prime}} + {N_{sc}^{RB}n_{PRB}} + k^{\prime}}};\mspace{79mu}{k^{\prime} = \left\{ {{\begin{matrix}1 & {p \in \left\{ {7,8,11,13} \right\}} \\0 & {{p \in \left\{ {9,10,12,14} \right\}};}\end{matrix}l} = \left\{ {{\begin{matrix}{{l^{\prime}{mod}\; 2} + 2} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 3},4,{8\mspace{14mu}{or}\mspace{14mu} 9}} \\{{l^{\prime}{mod}\; 2} + 2 + {3\left\lfloor {l^{\prime}/2} \right\rfloor}} & {{{if}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1},2,{6\mspace{14mu}{or}\mspace{14mu} 7}} \\{{l^{\prime}{mod}\; 2} + 5} & {{{if}\mspace{14mu}{not}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}};}\end{matrix}l^{\prime}} = \left\{ \begin{matrix}{0,1,2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0\mspace{14mu}{and}\mspace{14mu}{in}\mspace{14mu} a\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,\mspace{11mu}{{or}\mspace{14mu} 7}} \\{0,1} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {0{\mspace{11mu}\;}{and}\mspace{14mu}{not}\mspace{14mu}{in}{\mspace{11mu}\;}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{{or}\mspace{14mu} 7};{and}}} \\{2,3} & {{{{if}\mspace{14mu} n_{s}\mspace{14mu}{mod}\; 2} = {1{\mspace{11mu}\;}{and}\mspace{14mu}{not}{\mspace{11mu}\;}{in}\mspace{14mu}{special}\mspace{14mu}{subframe}\mspace{14mu}{with}\mspace{14mu}{configuration}\mspace{14mu} 1}},2,6,{{or}\mspace{14mu} 7}}\end{matrix} \right.} \right.} \right.}} \right.}$

Example 35 includes the apparatus of any of examples 32-34, wherein thecommon scrambling sequence is based on a virtual cell identifier.

Example 36 includes a method comprising: assuming, by a user equipment,a reference signal sequence received for a first antenna port forcommunications between the UE and an enhanced node B is also used forcommunications of a second antenna port; performing a blind decodingoperation for enhanced physical downlink control channel (EPDCCH) basedon said assuming.

Example 37 includes the method of example 36, further comprising:receiving the reference signal sequence for the first antenna port on anorthogonal frequency division multiplexing (OFDM) symbol; and estimatinga channel for the first antenna port for the UE based on receiving ofthe reference signal sequence and assuming the reference signal sequenceis also used for communications of a second antenna port.

Example 38 includes the method of example 37, further comprising:compensating a received signal based on the estimating of the channel.

What is claimed is:
 1. An apparatus to be employed in an enhance node B(eNB), the apparatus comprising: scrambling circuitry to receive a bitsequence that includes downlink control information (DCI) to betransmitted on an enhanced physical downlink control channel (EPDCCH)and to scramble the bit sequence based on a cell identifier to provide ascrambled bit sequence; and modulating circuitry coupled with thescrambling circuitry to receive the scrambled bits and to modulate thescrambled bits, with a quadrature phase shift keying modulation scheme,to provide a block of complex-valued modulation symbols, wherein thecell identifier is a virtual cell identifier; the DCI is to betransmitted in a first EPDCCH set; the virtual cell identifiercorresponds to the first EPDDCH set; and the scrambling circuitry is toscramble the DCI bits based on a scrambling initialization seed c_(int)given byc _(int) =└n _(s)/2┘*2⁹ +N _(ID) ^(ePDCCH) where n_(s) is a slot numberwithin a radio frame and N_(ID) ^(ePDCCH) is the virtual cellidentifier.
 2. The apparatus of claim 1, wherein the cell identifier isa provided to the scrambling circuitry by a radio resource controllayer.
 3. The apparatus of claim 2, further comprising: a referencesignal (RS) generator to generate demodulation reference signalsassociated with the EPDCCH based on the virtual cell identifier.
 4. Theapparatus of claim 1, further comprising: cyclic redundancy check (CRC)generating and masking circuitry to generate a bit sequence thatincludes DCI and CRC bits and to mask the bit sequence based on a radionetwork temporary identity (RNTI) of a user equipment that is anintended recipient of the DCI.
 5. The apparatus of claim 1, wherein thecell identifier is configured by radio resource control (RRC) signaling.6. The apparatus of claim 1, wherein the apparatus is a mobile devicethat includes a touchscreen display and one or more cameras.